What does an increasing number of cognitive disease diagnoses mean for probate disputes?
Capacity-related challenges lie at the heart of many contentious probate disputes. In England and Wales, ‘capacity’ refers to an individual’s ability to make a specific decision at the time it is required.
Although the governing legal principles are well established – principally under the Mental Capacity Act 2005 (MCA) and its section 3 diagnostic and functional tests – their application in probate litigation is often far from straightforward. In the testamentary context, this framework operates alongside the common law test in Banks v Goodfellow, which remains the touchstone for assessing capacity to make a will.
The challenge becomes particularly acute where the deceased was living with dementia. Approximately 982,000 people are currently living with dementia in the UK, a figure projected to rise to 1.4 million by 2040. As diagnoses increase in line with longer life expectancies, probate practitioners are encountering dementia-related capacity challenges with growing frequency.
Under the MCA, a person lacks capacity if they are unable to understand, retain, use or weigh relevant information, or to communicate their decision. In practice, however, these statutory criteria frequently overlap with the functional impairments associated with progressive cognitive diseases. This convergence can make it difficult to disentangle the existence of a diagnosis from its actual impact on an individual’s decision-making at a specific point in time.
Recent litigation trends suggest that this difficulty is increasingly translating into disputes. Litigation intelligence provider Solomonic reports that the final quarter of 2025 saw the highest number of probate claims issued in the High Court in the past decade, representing a 49.1% increase since 2020. With longer life expectancies, more complex family structures, and a growing financial reliance on inheritance among younger generations, probate disputes show little sign of abating. Notably, around 40% of claims issued in 2025 raised lack of testamentary capacity as a central issue.
In practical terms, the rise in cognitive disease diagnoses is increasing both the evidential and financial complexity of probate disputes. Parties are placing greater emphasis on contemporaneous documentary evidence, including solicitor attendance notes, medical records, and testamentary instructions, as well as retrospective expert evidence addressing capacity at the relevant time. These cases are therefore becoming more document-heavy and expert-driven, often leading to increased costs and longer-running disputes. The focus has shifted away from whether a diagnosis existed to a more nuanced analysis of its functional impact, with disputes frequently turning on the quality and detail of the available evidence.
Against this backdrop, the High Court has provided recent guidance on how dementia diagnoses should be approached in capacity challenges. In Parfitt v Jones & Wilkes, the testatrix’s daughter argued that her mother’s diagnosis of progressive dementia meant she lacked capacity to execute her 2008 will. The claim failed, with the court emphasising that capacity may fluctuate, even in the presence of cognitive decline.
Similarly, in Scott v Scott, the court rejected a challenge to a series of wills notwithstanding the testator’s diagnosis of frontotemporal dementia. Having analysed detailed attendance notes, GP records, and expert evidence from related Court of Protection proceedings, the judge reaffirmed that a diagnosis alone is insufficient to establish incapacity.
These decisions underscore a consistent judicial message: it is not the label of dementia that is determinative, but its functional effect at the precise time the will was executed.
An increase in cognitive disease diagnoses is also shaping will-drafting practices. Practitioners are placing greater emphasis on protective measures, including comprehensive attendance notes and, where appropriate, adherence to the so-called ‘golden rule’ of obtaining contemporaneous medical input when capacity may be in doubt. This reflects a growing recognition that careful preparation during the will-making process can significantly reduce the risk of future disputes, or at least strengthen the evidential position should a challenge arise.
The broader implication is that probate disputes are not simply becoming more frequent, but more complex and evidentially intensive. As the population ages and diagnoses of cognitive disease continue to rise, the distinction between diagnosis and decision-specific capacity will become increasingly central. For practitioners and litigants alike, the key issue will remain not whether a testator had a medical condition, but whether they retained the ability to understand and give effect to their testamentary intentions at the critical moment.